Anti-cloning method

ABSTRACT

The objective of the present invention is to propose a method that allows preventing the use of more than one identical security module for the identification and use of resources administered by an operating centre. This objective is achieved by an anti-cloning method based on the memorisation of the identification numbers of the user units connected to said security module.  
     During a connection with an operating centre these numbers are transmitted and compared with the numbers of a previous transmission. Differences are accepted as long as new numbers are added to a list previously transmitted. The security module is declared invalid if the numbers previously memorised are not included in the transmitted numbers.

[0001] The present invention concerns a method for detecting a duplication of a security module, particularly during the interaction of this security module with several user units.

[0002] These user units are connected to one or several networks proposing products or services. These products or services being subject to a conditional use, the use of these products is subject to a control, this is why these units have a security module in charge of the identification and management of the access authorisation to said networks.

[0003] These user units are presented in several forms, for example a pay-television decoder, a computer, even a mobile phone, a palmtop, a PDA, a radio, a television, a multimedia station, an automatic teller machine.

[0004] This security module is generally presented in the form of a smart card, a credit card or a SIM card, comprising a cryptographic processor. This card allows to supply the necessary information for identifying itself on the considered network by means of decryption operations using keys stored in the memory of the cryptographic processor reputed inviolable.

[0005] This security module can be in charge of exchanging confidential information with the user unit, for example when producing the key that starts the cryptographic operations associated to the identification or the payment of a product.

[0006] These security modules can be connected to several user units according to the user's needs. Such a use is admitted by the administrator of the network, and this is why the security module is generally moveable. This situation is found in the field of pay television or that of mobile phones.

[0007] Due to the value that this security module represents, particularly in electronic purse applications, the temptation is great for fraudsters to reproduce identically these modules.

[0008] Although the operating centre is able to detect the simultaneous use of two modules having the same serial number, if this use is done at different moments it is hardly possible for the operating centre to know if it is of the same module or of a clone.

[0009] A first solution is described in the document U.S. Pat. No. 4,672,533 and proposes to create a session number that must change with each connection with the operating centre. It is a previous identification to all transactions and although it answers the need to detect copies of the cards it only allows to function in an environment in which the on-line connection with the operating centre is obligatory.

[0010] The objective of the present invention is to propose a method that allows preventing the use of more than one identical security module for the identification and use of resources administered by at least one operating centre.

[0011] This objective is achieved by an anti-cloning control method of a security module comprising at least one unique identification number destined to be connected to a user unit comprising at least one unique identification number, this unit being able to be connected to an operating centre, this method comprising the following steps:

[0012] collecting by the security module the unique identification number of each user unit to which said module is connected,

[0013] upon request of the operating centre transmitting the unique identification number of the security module and the unique identifications numbers specific to the user units previously connected to this security module,

[0014] comparing by the operating centre these user units identifications numbers with the list previously memorised during the last connection with said centre,

[0015] authorising said security module if the list corresponds with the list previously memorised, if not authorising this security module provided that the unknown user unit identifications number follow the list previously memorised.

[0016] In this way the control of validity of the security module is not only based on the static data but also integrates a variable data that retraces the different user units that are used.

[0017] Thanks to this method a security module copied integrally differs from the original from its first use with a user unit.

[0018] Let us take for example a security module A that contains unique numbers i, j, k. During this first use, the memory zone of the security module will store the unique number l of the user unit UI. The original security unit will then contain the image i, j, k, l. A copy of this module (made before the first use described above) connected to a unit Up will contain the image i, j, k, p.

[0019] The first security module that will be connected to the operating centre by the user unit will transmit its information, for example i, j, k, l. If the clone module is equally connected, the image of the units connected to this module will necessarily contain i, j, k, l. In our case the member l is absent and indicates that this module is not the one previously connected. The clone is thus detected.

[0020] According to the chosen control protocol the operating centre, in case it detects such a module, can declare this security module invalid, blocking the use of the true module for the same occasion.

[0021] According to an embodiment it is enough to memorise two unique numbers to obtain the aimed objective, that is, the number of the current user unit and the number of the previous user unit. When the security module is moved to another user unit the current number becomes the previous number, the user unit number becoming the new current number.

[0022] Thanks to this method a security module can immediately become operational with a user unit without demanding an authorisation by an operating centre. A link with the operating centre can be carried out every n transactions, according to the duration of use, randomly, or on request of the operating centre. If the memory of the security module is full, a demand can be made that a connection be carried out with the operating centre before liberating space in the memory.

[0023] This invention can thus cover the case where a user unit would function without link with an operating centre. This can be the case of pay terminals limited to small amounts or of access to services such as pay television or the reception of numerical radio (DAB) for example. In this case the speed of availability is an asset to convince the user of using this type of services and it is acceptable to only carry out sporadic controls. When the user connects a ticket distributor which has a on-line communication with the centre, the verification is done at that moment.

[0024] This configuration will be advantageously described by FIGS. 1 to 3 that represent the memory zone of a security module.

[0025] Let us take for example FIG. 1, of a module N comprising two zones, one for the number of the current user unit Cn, the other for the previous terminal number C-1.

[0026] In the module N is the user unit number C in the previous zone C-1 and the user unit number D in the current zone Cn.

[0027] Let us take for example a connection of this security module to a first user unit E and then a second unit F. The memory of the module will contain the identification numbers such as illustrated by FIG. 2. The current zone Cn contains the user identification F.

[0028] During a connection with an operating centre these numbers A to F are transmitted and memorised in the centre for control. The previous memorised image contained the identification numbers A to D and there is then the identity between the memorised image and a part of the transmitted numbers.

[0029] It should be noted that according to the invention it is not necessary to connect with the operating centre with each new connection with the user unit. The control can be carried out sporadically, randomly, or upon demand of the operating centre.

[0030] A module that has been cloned in the state of FIG. 1 or with the numbers A to D and that has been connected to a user unit K presents a memory zone such as illustrated in FIG. 3.

[0031] When this information A to D, K is transmitted to the operating centre the member K is unknown and does not follow the previous image which is the user identification F. The operating centre can then deduct that there are two security modules with the same single number.

[0032] According to a simplified embodiment of the invention it is not necessary to keep the user identification numbers after a positive control. Only the last numbers are kept as a trace of the previous connections with the user units. By “last” we understand for example the last two or three.

[0033] From this fact it will be enough that in the subsequently transmitted numbers we find these last numbers to follow the trace of this module.

[0034] According to our previous example, once the module of FIG. 1 is accepted by the operating centre, the numbers A, B are erased from the memory zone of the module to keep only C, D.

[0035] This module is then connected to a unit E and then a unit F. These data C, D, E, F are transmitted to the operating centre for verification. The values C, D being present in the data previously memorised, the module is considered as valid and the user identifications E, F are erased.

[0036] In the case of FIG. 3 the cloned module is connected to the unit K that will transmit these data A, B, C, D, K to the operating centre. The latter looks for the presence of E, F according to the last connection, and from the fact that these user identifications are not present in the transmitted data, the centre can detect the presence of a falsified security module.

[0037] According to an embodiment the data exchanged between the security module and the user unit are encrypted by a pairing key, that is, a key specific to the couple security module/user unit. This key can by of several types, a secret symmetrical key or an asymmetrical key (public key, private key). Following the nature of the key it is possible to use this key as a single user identification such as described above to identify the user unit. In this case it is not the user unit in time as such that is identified but the couple formed by the security module and the user unit.

[0038] It is then possible to transmit all or part of this pairing key as a user identification. In fact for the identification operations it is possible to use a part of this key, particularly if we wish that this key is not divulged. According to a particular embodiment it is the version using a key pair public key/private key that is used as a pairing key (asymmetrical keys) and it is the public key that is used as a user identification. 

1. An anti-cloning control method of a security module comprising at least one unique identification number destined to be connected to a user unit comprising at least one unique identification number, this unit being able to be connected to an operating centre, this method comprising the following steps: collecting by the security module the unique identification number of each user unit to which said module is connected, upon request of the operating centre transmitting the unique identification number of the security module and the unique identification numbers specific to the user units previously connected to this security module, comparing by the operating centre these identification numbers with the list previously memorised during the last connection with said centre, authorising said security module if the list corresponds with the list previously memorised, if not authorising this security module provided that the unknown user identifications follow the list previously memorised.
 2. A method according to claim 1, characterised in that it consists in preventing access to resources administered by the operating centre if the last memorised identification number is not contained in the transmitted unique identification numbers.
 3. A method according to claim 1, characterised in that it consists in erasing the unique identification numbers of the user units in the security module excepting the last memorised one.
 4. A method according to claims 1 to 3, characterised in that the unique identification number is formed by all or part of a pairing key in charge of encrypting the data exchanged between the security module and the user unit.
 5. A method according to claim 4, characterised in that the pairing key is of the asymmetric type and that the unique identification number is represented by the public key. 